1. Fields of the Invention
The present invention relates to a process for producing optically active compounds by a biochemical method in which specific compounds having hydroxyl groups are reacted with esters in the presence of enzymes.
2. Description of the Prior Art
Optically active compounds represented by the general formula (I) are useful chemical compounds as starting materials of medical supplies, agricultural chemicals and the like. However, the compounds have optical isomers, so that they do not sufficiently exhibit their characteristics in many cases
unless either an R- or S-alcohol is purely contained. ##STR2## wherein Y is selected from the group consisting halogen atoms, alkyl groups having 1-3 carbon atoms, cyano groups, and trifluoromethyl groups, W is selected from the group consisting the following groups: ##STR3## wherein X.sup.1, X.sup.2, X.sup.3, X.sup.4 and X.sup.5 are selected from the group consisting hydrogen and halogen atoms, cyano, trifluoromethyl, amino, alkylamino, aryloxy, and the following goups: ##STR4## and alkyl and alkoxy groups having 1-20 carbon atoms, Z.sup.1, Z.sup.2, Z.sup.3, Z.sup.4 and Z.sup.5 are selected from the group consisting hydrogen and halogen atoms, cyano, trifuluoromethyl, and amino groups and alkylamino, alkyl and alkoxy groups having 1-20 carbon atoms,
and halogen atoms, cyano, trifluoromethyl and amino groups and alkylamino and alkyloxycarbonyl groups in which alkyl groups have 1-20 carbon atoms, R is methylene and n is 0 or 1.
For the above reason, in order to an obtain optically active substance, it is needed to optically resolve a racemate which is obtained by a common method of synthetic chemical technique, to conduct asymmetric synthesis or to convert from an optically active starting material by a stereochemical synthetic method. In many cases, the processe is troublesome and disadvantageous industrially.
Accordingly, it is desired to develop a technique for obtaining optically active compounds by an industrially advantageous method.
As a known biochmical technique, for example, there is a method described in Japanese Publication of Unexamined Patent Application No. 59-205989 in which a racemic ester is hydrolyzed with a lipase and an desired alcohol is obtained. In this case, the racemic ester is often insoluble in water, so that it is necessary to emulsify or stir vigorously by using a large quantity of water. Klibanov et al. reported a method in which enzyme powder was directly added into a reaction system (J. Am. Chem. Soc., 107, 7072 (1985). In this case, esters for transesterification are extremely limited and 2,2,2-trichloroethyl butyrate is used as the ester.
Furthermore, it is essential to use an organic solvent, such as heptane or ether which has many problems when it is used industrially.
The inventors of the present invention conducted research for resolving the above problems and obtaining a process for producing optically active compounds represented by the above general formula (I) by an advantageous industrial method and then found that racemic compounds of raw materials are efficiently resolved to optically active compounds and their antipodes, namely optically active esters, by a biochemical transesterification reaction.